The purpose of this study is to investigate the function of the 3' terminus of both AA-tRNA and peptidyl-tRNA in ribosomal protein synthesis and to study the properties and functions of the ribosomal recognition sites involved in binding in the 3' terminus of AA-tRNA and peptidyl- tRNA. The chemical syntheses of 2'(3')-O-aminoacyl, 2'(3')-O-(N- acylaminoacyl) and 2'(3')-O-peptidyl oligoribonucleotides having different chain lengths, base sequences and amino acids will be undertaken, and these compounds will be used to study the substrate specificity of ribosomal peptidyl transferase at the A and P sites. The biochemical studies will be carried out using several ribosomal transfer and binding systems. The substrate specificity of certain antibiotics that inhibit protein biosynthesis will also be investigated.